1. Field of the Invention
This invention relates generally to molding. In particular, this invention relates to mold assemblies having ejector device housings.
2. Description of Related Art
It is known in the art of molding, for example injection molding, to use mold assemblies comprising mating mold components defining one or more mold cavities. In addition to the mating mold components, mold assemblies comprise mounting sub-assemblies constructed for mounting to members of the press or clamp unit of a molding machine, the clamp unit being operated to close the mold assembly for molding and open the mold assembly to remove molded articles. It is further known to provide mold assemblies having ejector devices for dislodging molded material from the mating mold components. Advantageously, components of the ejector device are surrounded on at least four sides by members of a mounting sub-assembly defining a so-called “ejector housing 5” or “ejector box”. Referring to FIG. 1, a mold sub-assembly 10 comprises an assembly mounting plate 12, right and left side die retention plates 14 and 16, respectively, and a die mounting plate 18 for supporting a mold component. As shown, left and right side die retention plates space die mounting plate 18 from assembly mounting plate 12. Advantageously, left and right side retention plates have grooves for receiving projecting ears of die mounting plate 18 facilitating removal and insertion of die mounting plates with mold components attached from and into a subassembly of assembly mounting plate 12 and die retention plates 14 and 16. Elements of an ejector device are movably supported within the ejector housing 5 created by assembly mounting plate 12, die retention plates 14 and 16 and die mounting plate 18. Ejector device elements within the ejector housing 5 comprise ejector pins 20, ejector plate 24 for supporting ejector pins 20 and pin retainer plate 22 for retaining ejector pins 20 on ejector plate 24. Ends of ejector pins 20 pass through die mounting plate 18 and protrude into a mold component mounted thereto. Movement of ejector plate 24 toward die mounting plate 18 advances the projecting ends of ejector pins 20 to dislodge a molded article and sprue from the mold component mounted thereon. Commonly, one or more ejector rods (not shown) pass through openings in assembly mounting plate 12 and engage the assembly of ejector plate 20 and pin retainer plate 22 to effect movement thereof. As shown, functional elements of assembly mounting plate 12 and die retention plate 18 involve surfaces, bores and the like machined in the faces of the plates or through the plates. Similarly, functional elements of die retention plates 14 and 16 involve surfaces, bores and the like machined in the faces thereof. The manufacture of these plates does not require machining in or of the ends thereof other than to produce plates of the desired overall dimensions. Hence, the machining of these plates can be completed without arranging the plate being machined to perform machining operations into the ends thereof.
The ejector housing 5 is advantageously open on at least one side of the sub-assembly, the periphery of the openings of the ejector housing being defined by ends of mold assembly members defining the ejector housing. Advantageously at least one opening of the ejector housing is left exposed or accessible through openings in the machine as the sub-assembly is mounted to a machine member. Hence, with the sub-assembly installed in a molding machine press, access is provided to the ejector device components within the ejector housing 5 through the ejector housing opening. It is known to provide ejector housing covers for covering, at least partially, the openings of ejector housing 5 to allow guarded examination of the interior of the ejector housing. Such covers are provided with openings through which an examination can be made but which are effective to block a user from reaching pinch points within the housing. Known ejector housing covers are attached to the mold assembly by fasteners accessible from the face of the cover. Hence the fasteners engage the ends of the mold assembly members defining the ejector housing 5, requiring machining into those ends. This arrangement presents a disadvantage in the manufacture of the mold assembly members since the required machining necessitates a set-up different from set-ups used for other machining operations performed on the mold assembly members. Further, the known arrangement for attaching the ejector housing cover allows removal of the cover with the mold assembly installed in a machine, increasing the potential for operation of the machine with the ejector housing cover removed.